On 12/13/2011 02:11 PM, Jose Fonseca wrote: > ----- Original Message ----- >> This is an updated version of the patch set I sent to the list a few >> hours >> ago. >> There is now a TGSI property called >> TGSI_PROPERTY_NUM_CLIP_DISTANCES >> that drivers can use to determine how many of the 8 available clip >> distances >> are actually used by a shader. > Can't the info in TGSI_PROPERTY_NUM_CLIP_DISTANCES be easily derived from the > shader, and queried through src/gallium/auxiliary/tgsi/tgsi_scan.h ?
No. The clip distances can be indirectly addressed (there are up to 2 of them in vec4 form for a total of 8 floats), which makes it impossible to determine which ones are used by analyzing the shader. > Could you also elaborate on why TGSI_SEMANTIC_CLIPDIST is useful for the > drivers? I personally don't have nothing against it, but just like to > understand why it makes a difference. > > Jose Unless my understanding of clip distances is wrong, the GPU uses clip distances to decide whether a vertex should be clipped, and thus needs to know which of the vertex shader outputs are clip distances. Bryan _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
